Noise and particle condensation

H. Umezawa*, Y. Yamanaka

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)


This paper is aimed to clarify the appearance of non-quantum noises in quantum systems in various subjects from a unified viewpoint. Examples taken are the squeezed state in quantum optics, the Hawking radiation around the black hole and thermo field dynamics (TFD) in thermal quantum field theory. Under the use of mathematical formulation of TFD, the origin of noises is traced to the Bogoliubov transformation, i.e., the pair condensation of bare particles in the physical vacua. Detailed analysis of the noise energy reveals a crucial distinction among them: Calling the operator generating the noise energy the noise generator, we find two cases, dynamical and spontaneous, depending on whether the noise generator is part of the Hamiltonian or not. The squeezed state belongs to the former, TFD does to the latter.

Original languageEnglish
Pages (from-to)291-305
Number of pages15
JournalPhysica A: Statistical Mechanics and its Applications
Issue number2
Publication statusPublished - 1991 Jan 1
Externally publishedYes

ASJC Scopus subject areas

  • Statistics and Probability
  • Condensed Matter Physics


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